Covered on Genetics Home Reference: autoimmune lymphoproliferative syndromebreast cancerFrom NCBI Gene: Caspase-8 deficiencyHepatocellular carcinomaFamilial cancer of breastLung cancerFrom UniProt: Caspase-8 deficiency (CASP8D): Disorder resembling autoimmune lymphoproliferative syndrome (ALPS). It is characterized by lymphadenopathy, splenomegaly, and defective CD95-induced apoptosis of peripheral blood lymphocytes (PBLs). It leads to defects in activation of T-lymphocytes, B-lymphocytes, and natural killer cells leading to immunodeficiency characterized by recurrent sinopulmonary and herpes simplex virus infections and poor responses to immunization. [MIM:607271]

     From NCBI Gene: This gene encodes a member of the cysteine-aspartic acid protease (caspase) family. Sequential activation of caspases plays a central role in the execution-phase of cell apoptosis. Caspases exist as inactive proenzymes composed of a prodomain, a large protease subunit, and a small protease subunit. Activation of caspases requires proteolytic processing at conserved internal aspartic residues to generate a heterodimeric enzyme consisting of the large and small subunits. This protein is involved in the programmed cell death induced by Fas and various apoptotic stimuli. The N-terminal FADD-like death effector domain of this protein suggests that it may interact with Fas-interacting protein FADD. This protein was detected in the insoluble fraction of the affected brain region from Huntington disease patients but not in those from normal controls, which implicated the role in neurodegenerative diseases. Many alternatively spliced transcript variants encoding different isoforms have been described, although not all variants have had their full-length sequences determined. [provided by RefSeq, Jul 2008] From UniProt: Most upstream protease of the activation cascade of caspases responsible for the TNFRSF6/FAS mediated and TNFRSF1A induced cell death. Binding to the adapter molecule FADD recruits it to either receptor. The resulting aggregate called death-inducing signaling complex (DISC) performs CASP8 proteolytic activation. The active dimeric enzyme is then liberated from the DISC and free to activate downstream apoptotic proteases. Proteolytic fragments of the N-terminal propeptide (termed CAP3, CAP5 and CAP6) are likely retained in the DISC. Cleaves and activates CASP3, CASP4, CASP6, CASP7, CASP9 and CASP10. May participate in the GZMB apoptotic pathways. Cleaves ADPRT. Hydrolyzes the small-molecule substrate, Ac-Asp-Glu-Val-Asp-|-AMC. Likely target for the cowpox virus CRMA death inhibitory protein. Isoform 5, isoform 6, isoform 7 and isoform 8 lack the catalytic site and may interfere with the pro-apoptotic activity of the complex.

The following transcription factors affect gene expression:

• IRF-1
• IRF-2
• p53
• STAT1
• STAT1alpha
• STAT1beta
• Sp1
• FOXO1a
• FOXO1
• STAT3

Tissue specificity:

Isoform 1, isoform 5 and isoform 7 are expressed in a wide variety of tissues. Highest expression in peripheral blood leukocytes, spleen, thymus and liver. Barely detectable in brain, testis and skeletal muscle.

Enzyme Regulation:

Inhibited by the effector protein NleF that is produced by pathogenic E.coli; this inhibits apoptosis.

Molecular Function:

• Cysteine-Type Endopeptidase Activity
• Peptidase Activity
• Cysteine-Type Peptidase Activity
• Ubiquitin Protein Ligase Binding
• Death Effector Domain Binding
• Identical Protein Binding
• Scaffold Protein Binding
• Cysteine-Type Endopeptidase Activity Involved In Apoptotic Process
• Cysteine-Type Endopeptidase Activity Involved In Apoptotic Signaling Pathway

Biological Processes:

• Proteolysis
• Apoptotic Process
• Activation Of Cysteine-Type Endopeptidase Activity Involved In Apoptotic Process
• Cellular Component Disassembly Involved In Execution Phase Of Apoptosis
• Cell Surface Receptor Signaling Pathway
• Response To Cold
• Regulation Of Tumor Necrosis Factor-Mediated Signaling Pathway
• Regulation Of Necrotic Cell Death
• Natural Killer Cell Activation
• Macrophage Differentiation
• Response To Cobalt Ion
• Response To Estradiol
• Response To Lipopolysaccharide
• Response To Tumor Necrosis Factor
• Trif-Dependent Toll-Like Receptor Signaling Pathway
• Trail-Activated Apoptotic Signaling Pathway
• Suppression By Virus Of Host Cysteine-Type Endopeptidase Activity Involved In Apoptotic Process
• T Cell Activation
• B Cell Activation
• Positive Regulation Of I-Kappab Kinase/Nf-Kappab Signaling
• Negative Regulation Of I-Kappab Kinase/Nf-Kappab Signaling
• Response To Ethanol
• Positive Regulation Of Macrophage Differentiation
• Positive Regulation Of Proteolysis
• Response To Antibiotic
• Protein Heterooligomerization
• Proteolysis Involved In Cellular Protein Catabolic Process
• Syncytiotrophoblast Cell Differentiation Involved In Labyrinthine Layer Development
• Nucleotide-Binding Oligomerization Domain Containing Signaling Pathway
• Cellular Response To Mechanical Stimulus
• Cellular Response To Organic Cyclic Compound
• Death-Inducing Signaling Complex Assembly
• Apoptotic Signaling Pathway
• Extrinsic Apoptotic Signaling Pathway
• Execution Phase Of Apoptosis
• Activation Of Cysteine-Type Endopeptidase Activity
• Activation Of Cysteine-Type Endopeptidase Activity Involved In Apoptotic Signaling Pathway
• Positive Regulation Of Protein Insertion Into Mitochondrial Membrane Involved In Apoptotic Signaling Pathway
• Regulation Of Extrinsic Apoptotic Signaling Pathway Via Death Domain Receptors
• Negative Regulation Of Extrinsic Apoptotic Signaling Pathway Via Death Domain Receptors